The fast food or Western diet is characterized as high in saturated fat and simple sugars and almost completely lacking in fiber. It’s a great recipe for weight gain, which is why nearly 40 percent of American adults are obese. It’s also a great way to trigger systematic inflammation. Short-term inflammation is a normal part of healing or immune system protection, but chronic inflammation shortens lifespans and increases the risk of developing diseases like cancer, dementia, heart disease, muscle loss and more.

A two tiered attack

The two pillars of the immune system are the innate immune system and the adaptive immune system. Like it sounds, the adaptive system is the part that remembers specific pathogens and develops long-lasting defenses against that particular invader. A good example of this is once you catch the measles, your adaptive immune system develops defenses that prevents it from returning.

The innate system is the fast-acting response to generalized pathogens and injuries. Its purpose is to quickly isolate the area and summon other immune cells to finish the job. One way it does this is through inflammation. The chemicals released actually establish a physical barrier to prevent an infection from spreading while simultaneously stimulating the disposal of invaders and triggering healing for any damaged cells.

We previously thought the innate immune system doesn’t learn in response to invaders, but new findings show that the innate immune system remains in a more activated state after infection so that it can more quickly respond to secondary infections. Once again, this was historically a good thing, but another new study found how the typical Western diet can trigger this “innate immune training” and cause increased inflammation from diet alone.

Like an infection

The study put mice on a fast food or Western diet which was high in saturated fat and sugar and low in fiber. The mice developed a strong inflammatory response as if they were suffering from an infection. Genetic testing of immune precursor cells in their bone marrow found activation of NLRP3 inflammasomes. The purpose of these molecules is to detect when something is disturbing the homeostasis of your cells. Inflammasomes are interesting because they detect things such as bacterial remnants like lipopolysaccharides (LPS), virus RNA, or ATP that leaked out of damaged cells. The researchers weren’t positive of the exact reason this pathway was activated. One possible cause is the lack of fiber caused the lining of the gut to erode. The immune system is then able to attack the good bacteria that it’s now detecting. Remnants of their destruction (like LPS) can then enter the system and trigger systematic inflammation.

Altered genetic experession

When the mice were switched back to a normal chow diet, the inflammation subsided (because increased fiber strengthened the gut barrier again), but not the innate immune training. The researchers found that even four weeks after returning to a normal diet, the genes expressed in the immune precursor cells were still activated. This meant that when they tested immune reactions to small stimuli, they generated a much stronger inflammatory response.

Eat fiber with your junk food

I will admit this last bit of advice is conjecture on my part but it goes along with so much research we’re seeing on the microbiome. A recent article in Nature Microbiology characterized the nutritional preferences of 96 different gut bacterial strains. My biggest takeaway from their analysis came from Kiran Patil who said, “We were surprised to find new bacteria with the capability to utilize mucin, the protein that makes up mucus. These bacteria can contribute to inflammation and infection by weakening the protective mucus barrier lining the gut.”

I’ve said it many times before that you need to eat fiber so the beneficial bacteria in your gut can feed your intestinal cells the short chain fatty acids they need to make mucin. When you starve those same bacteria, they eat the mucin instead and trigger a massive inflammation response by your immune system. This latest study shows that even more beneficial bacteria are capable of doing this than we previously thought.

Another study looked at monounsaturated fats in relation to heart disease and found that monounsaturated fats from plant sources decrease the risk of heart disease while the same type of fat from animal sources does not. There are other micronutrients and polyphenols that may contribute to the difference as well, but once again, the presence of fiber results in significant health improvements.

Fiber is more than just a way to fill you up or keep you regular. I don’t expect you to eat perfect all the time, but add vital fiber to your crappy Western diet as much as possible to keep rampant inflammation in check.